A Central District Court jury today found a Chelsea man not guilty of vehicular homicide by driving negligently in connection with an accident on the Massachusetts Turnpike in Grafton in which a Whitinsville mechanic was killed in 2009.

Following testimony from seven prosecution witnesses that began Monday, the jury deliberated less than four hours before finding Kenneth Lava, 64, not guilty.

He was driving a large U-Haul van leased to his employer, Kayem Foods Inc., when Dennis Scott, 36, of Whitinsville was struck and killed.

Mr. Scott, a master mechanic, had just finished repairing a disabled tractor trailer in the breakdown lane.

Assistant Worcester County District Attorney David P. Feraco maintained that Mr. Lava was driving negligently because his van entered the breakdown lane and struck the victim.

Mr. Lava’s attorney, Carmine P Lepore of Revere, contended that it was a tragic accident, but that his client had not been negligent because Mr. Scott, a giant of a man at 6 feet and more than 300 pounds, was partly on the roadway.

Before the return of the not guilty verdict, Mr. Lava was found responsible for a civil motor infraction of marked lanes violation. He was fined $100.